JP2015520045A - Composite shape memory material - Google Patents

Abstract

The multilayered composite shape memory material comprises a first polymer layer of co-extruded first polymer material and a second polymer layer of second polymer material. The composite shape memory material after thermomechanical programming can undergo a shape transition from a temporary shape to a permanent shape due to at least one temperature induction. The first polymer layer constitutes a hard segment of shape memory material that imparts a permanent shape to the shape memory material, and the second polymer layer constitutes a switching segment of shape memory material that imparts a temporary shape to the shape memory material. [Selection] Figure 1

Description

This application claims priority to US Provisional Application No. 61 / 636,039, filed Apr. 20, 2012, the subject matter of which is incorporated herein by reference in its entirety. Is done.

Government Funding This invention was made with government support under grant number RES501499 awarded by the National Science Foundation. The US government may have certain rights to the invention.

  Shape memory polymers (SMPs) are active materials that can exhibit at least two shape configurations, one of which is a unique permanent shape and the other shape configuration is a separate temporary or It is a fixed shape. The temporary or fixed shape most commonly occurs or shrinks in a thermal transition such as a glass transition or melting. The temporary shape is obtained by exposing the SMP to an external stimulus, most often heat, that places the SMP component in either a rubbery or molten state that exceeds its transition temperature. Temporary shapes are formed by vitrification or crystallization of the rubbery or molten SMP component by deformation during the rubbery or molten state and then cooling below the transition temperature under the imposed stress. Fixed. The SMP then returns to its original permanent shape upon exposure to external stimuli.

  Most SMPs exhibit a dual shape memory behavior with two shape configurations, permanent and temporary, but some have two or more temporary shapes known as triple shape memories. This is particularly useful in medical and aerospace applications where there is a high demand for the ability to operate in a limited space. SMP also has the unique ability to be remotely activated to avoid harm to the surrounding environment during operation and deployment. Exposure to heat, IR and UV radiation, currents, magnetic fields, chemicals, and moisture can act as stimuli to initiate shape recovery.

  The polymer structure and morphology provide a permanent and temporary network structure. Most SMPs are copolymers consisting of hard segments that create permanent memory shapes and switching domains that create temporary shapes. In order to exhibit shape memory behavior, copolymers often exhibit a phase separated structure. There are challenges in determining the copolymer composition that produces a structure capable of shape memory behavior.

  In order to maintain the storage network structure, the transitions of each copolymer block must be sufficiently separated. Further, in order to generate an SMP having good shape fixation and good shape recovery, it is necessary to balance the weight ratio of the storage network structure and the switching network structure. A high hard segment composition produces good shape recovery, but adversely affects shape fixing properties. Therefore, there is always a compromise between shape fixing and shape recovery.

  Current shape memory polymers are generally copolymers that are specifically synthesized for use as shape memory materials. This requires a thorough, time consuming and large amount of solvent process to produce SMP, often using additional solvent to cast or coat the SMP film after the process. Is done. These processes involve the use of large amounts, often expensive, flammable and harmful organic solvents. Also, these solvents are expensive not only when purchased, but also when discarded at the end of SMP processing. In many cases, solvent costs, including initial solvent purchases, solvent handling equipment, and solvent disposal equipment and processes are significant costs in the manufacture of polymers for shape memory applications.

  The copolymers used are often polyurethane, polyether, and polyester systems, but the block combinations for shape memory polymers are endless. Currently, the majority of SMPs are not produced on a large scale and / or are not commercially available, resulting in an expensive manufacturing process.

  Embodiments described herein relate to a multilayered composite shape memory material comprising a co-extruded first polymer layer of a first polymer material and a second polymer layer of a second polymer material. The first polymeric material and the second polymeric material can have different melting temperatures and / or glass transition temperatures. The composite shape memory material after thermomechanical programming can undergo a shape transition from a temporary shape to a permanent shape due to at least one temperature induction. The first polymer layer can constitute a hard segment of a shape memory material that gives the shape memory material a permanent shape, and the second polymer layer can be a switching segment of the shape memory material that gives the shape memory material a temporary shape. Can be configured.

  Other embodiments described herein relate to a method of manufacturing a multilayer shape memory material. The method includes coextruding a first polymeric material having a first glass transition or melting temperature and a second polymeric material having a second glass transition temperature different from the first glass transition and / or melting temperature, Forming a multilayered shape memory material. The multi-layer shape memory material after thermomechanical programming can undergo a shape transition from at least one temperature-induced temporary shape to a permanent shape.

Still other embodiments described herein relate to a multilayer shape memory material comprising a co-extruded, multilayered, mechanically deformable composite shape memory sheet or film. The multilayered and mechanically deformable composite shape memory sheet has a plurality of formulas (AB) _x (where x = 2 ⁿ and n is in the range of 1 to 18). At least two alternating layers (A) and (B) are provided. Layer (A) consists of polymer component (a), and layer (B) consists of polymer component (b). Polymer components (a) and (b) have different glass transitions and / or melting temperatures, and the multilayer shape memory material after thermomechanical programming is from at least one temperature-induced temporary shape to a permanent shape. Can cause a shape transition.

It is a figure which shows the general-view figure of the polymer composite shape memory material which concerns on 1 aspect of this application. It is a figure which shows the general-view figure of the multilayer composite shape memory material which concerns on another aspect of this application. FIG. 3 shows a schematic diagram of a layer multiplication coextrusion process for forced assembly of polymer layers according to one embodiment of the present application. FIG. 5 shows a schematic diagram of layer multiplication coextrusion for forced assembly of polymer layers according to another embodiment. It is a figure which shows the photograph of the co-extrusion multilayer strand which concerns on 1 aspect of this application. It is a figure which shows the photograph of the co-extrusion multilayer film which concerns on 1 aspect of this application. FIG. 7 shows plots representing (A) stress versus strain and (B) recovery rate for the film of FIG. (A) Films prepared from various PCL / PU melt blends with varying PCL / PU ratios, and (B) PCL / PU ratios in the films at 30/70, 50/50, and 70/30 FIG. 6 shows a plot representing the switching temperature of a multilayer film with 512 alternating PU / PCL layers as varied. It is a figure which shows the (A) schematic and (B) photograph of the coextruded multilayer film which concerns on another aspect of this application. FIG. 10 shows a plot representing stress versus strain for the film of FIG. 9 having various thicknesses. It is a figure which shows the schematic of the triple shape memory material which concerns on 1 aspect of this application.

  Embodiments described herein relate to polymeric composite shape memory materials and methods used to produce polymeric composite shape memory materials by a solvent-free process. As the polymer composite shape memory material produced by the method described herein, a commercially available polymer that has not been considered as a shape memory polymer (SMP) can be used. The polymer composite shape memory material (film, strand, or fiber) should be used for biomedical, aerospace, high performance packaging, and sensor applications by melt processing without any specialized synthesis or solvent. Can do.

  FIG. 1 is a schematic illustration of a polymer composite shape memory material 10 according to one embodiment of the present application. The polymer composite shape memory material 10 can undergo a shape transition from the temporary shape 16 to the permanent shape 18 due to at least one temperature induction. The polymer composite shape memory material 10 includes at least a first polymer layer 12 and a second polymer layer 14. The first polymer layer 12 is formed from a first polymer having a first glass transition temperature and a first melting temperature. In some embodiments, the first polymer layer 12 can constitute a hard segment of the shape memory material 10 that gives the shape memory material 10 a permanent shape 18. The second polymer layer 14 is formed from a second polymer having a second glass transition temperature and a second melting temperature different from the melting temperature and / or glass transition temperature of the first polymer material. In some embodiments, the second polymer layer 14 can constitute a switching segment of the shape memory material 10 that produces a temporary shape 18 of the shape memory material. The first polymer layer 12 and the second polymer layer 12 have dimensions similar to phase separated domains (eg, hard domains, crystalline domains, switching domains, and / or amorphous domains) in known shape memory polymers. Separate nanoscale or microscale polymer domains (eg, hard domains, crystalline domains, switching domains, and / or amorphous domains) that are on a scale can be constructed.

  In some embodiments, the first polymer material of the first polymer material is formed such that a polymer composite comprising the first polymer layer 12 and the second layer 14 is formed and the polymer composite exhibits shape memory behavior. The one glass transition temperature and / or the first melting temperature may be different from the second glass transition temperature and / or the second melting temperature of the second polymeric material, respectively. For example, when the polymeric composite shape memory material 10 is provided in the form of a film, strand, or other structure, at least two shape arrangements, one of which is a permanent shape 16 and the other shape arrangement is distinct. A temporary or fixed shape 18). The temporary or immobilized shape 18 is a thermal transition, such as a glass transition and / or a melting transition that is defined or determined by the glass transition temperature and / or melting temperature of the first polymeric material and the second polymeric material. Arises or shrinks in a general metastasis. The temporary shape 18 exposes the shape memory material 10 to an external stimulus such as heat and causes either the first polymer or the second polymer to exceed its transition temperature in an amorphous state, a rubbery state, or Obtained by placing in either melted state. Deformation during cooling to below the transition temperature under the amorphous state, rubbery state, or molten state and the imposed stress may result in an amorphous state, rubbery state of the first polymer material or the second polymer material. The temporary shape is fixed by vitrification or crystallization in a molten state. Subsequent exposure to external stimuli restores the composite shape memory material to its original permanent shape. Films and strands made using the polymer composite shape memory material can exhibit not only good shape fixation but also a 100% shape restoration rate upon thermal stimulation.

  In some embodiments, the first polymer layer 12 is rubbery to provide mechanical restoration and the second polymer layer 14 to allow freezing of the temporary shape for use in various applications. Are reversibly cross-linked physically or chemically. Alternatively, the second polymer layer 14 may be rubbery to provide mechanical restoration, and the first polymer layer may be physically loaded to allow freezing of the temporary shape for use in various applications. Alternatively, it can be chemically and reversibly cross-linked.

  In other embodiments, the first polymer layer 12 may be a generally crystalline hard layer with a defined melting point and the second polymer layer 14 has a defined glass transition temperature. In general, it may be an amorphous soft switching layer. Alternatively, the second polymer layer 14 may be a generally crystalline hard layer having a defined melting point, and the first polymer layer 12 typically has a defined glass transition temperature. It may be an amorphous soft switching layer. However, in some embodiments, the hard layer (s), whether the first polymer layer 12 or the second polymer layer 14, is amorphous and has a glass transition rather than a melting point. It may have a temperature. In other embodiments, the soft layer (s), whether the first polymer layer or the second polymer layer, is crystalline and has a melting point rather than a glass transition temperature. Good. The melting point or glass transition temperature of the soft layer (s) may be substantially less than the melting point or glass transition temperature of the hard layer.

  The first polymer material used to form the first polymer layer 12 and the second polymer material used to form the second polymer layer 14 can be melt extruded to form a composite shape memory material. Any polymer may be mentioned. The first polymer material and the second polymer material have different glass transition temperatures and / or melting temperatures, and a composite of the first polymer layer and the second polymer layer is formed during melt extrusion. Formed and the composite should be selected to exhibit shape memory properties. The first polymeric material may be incompatible or partially compatible with the second polymeric material when coextruded so as to form separate layers in the composite shape memory material 10. It should be appreciated that the polymeric shape memory material may be manufactured by providing one or more additional layers formed from a first polymeric material, a second polymeric material, or a different polymeric material. .

  In some embodiments, the first polymeric material and the second polymeric material are not shape memory polymers. In other words, the first polymer material and the second polymer material do not exhibit shape memory characteristics when individually structured, that is, separately molded to have a structure. It is the different properties of the polymers (eg, glass transition) used to form at least the first polymer layer and the second polymer layer that impart the shape memory behavior or properties to the composite shape memory materials described herein. Temperature, melting temperature, and crystallinity). This allows a wider range of polymers to be selected than the range of polymers that have been used to form shape memory materials with shape memory polymers to form composite shape memory materials. However, it should be appreciated that at least the first polymeric material or the second polymeric material may potentially be a shape memory polymer.

  Examples of polymeric materials that can potentially be used for the first and second polymeric materials include, but are not limited to, poly (ethylene terephthalate) (PET), poly (butylene terephthalate), poly (ethylene terephthalate glycol). ), Polycaprolactone (PCL), and melt extrudable polyesters such as poly (ethylene naphthalate); 2,6-, 1,4-, 1,5-, 2,7-, and 2,3-polyethylene naphthalate Polynaphthalates such as phthalates and isomers thereof; Polyalkylene terephthalates such as polyethylene terephthalate, polybutylene terephthalate, and poly-1,4-cyclohexanedimethylene terephthalate; Polyimides such as polyacrylimide; Polyetherimide; Polyurethane, atactic, Iso Styrenic polymers such as tactic and syndiotactic polystyrene, α-methyl-polystyrene, para-methyl-polystyrene; polycarbonate (PC) such as bisphenol-A-polycarbonate; poly (isobutyl methacrylate), poly (propyl methacrylate), poly ( Poly (meth) acrylates such as ethyl methacrylate), poly (methyl methacrylate), poly (butyl acrylate) and poly (methyl acrylate) (the term “(meth) acrylate” is used herein to indicate acrylate or methacrylate). Cellulose derivatives such as ethyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, and cellulose nitrate; polyalkylene polymers such as polyethylene; Polyethylene, such as mer, polyethylene and polyethylene oxide (PEO); polypropylene, polybutylene, polyisobutylene, and poly (4-methyl) pentene; perfluoroalkoxy resin, polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, polyfluoride Fluorinated polymers such as polyvinylidene chloride and polychlorotrifluoroethylene and copolymers thereof; chlorinated polymers such as polydichlorostyrene, polyvinylidene chloride and polyvinyl chloride; polysulfone; polyethersulfone; polyacrylonitrile; nylon, nylon 6 , 6, polycaprolactam, and polyamides such as polyamide 6 (PA6); polyvinyl acetate; and polyether-amides. Other polymer materials include: acrylic rubber; isoprene (IR); isobutylene-isoprene (IIR); butadiene rubber (BR); butadiene-styrene-vinylpyridine (PSBR); butyl rubber; polyethylene; chloroprene (CR); Ethylene-propylene (EPM); ethylene-propylene-diene (EPDM); nitrile-butadiene (NBR); polyisoprene; silicone rubber; styrene-butadiene (SBR); and urethane rubber. Still other polymer materials include block or graft copolymers. In one example, the plurality of polymeric materials used to form the plurality of layers can be incompatible thermoplastic resins.

  Each individual layer 12, 14 may also contain two or more blends of the above polymers or copolymers. The components of the formulation are preferably substantially compatible with each other while still maintaining substantial incompatibility between layers 12,14. The polymeric material comprising the layers 12, 14 can also include organic or inorganic materials designed to modify the mechanical properties of the polymeric layer, including, for example, nanoparticle materials. As long as such polymeric materials (a), (b) are substantially incompatible upon coextrusion and form a separate layer or polymer region, any extrudable polymer is the first polymeric material ( It should be appreciated that it can potentially be used as a) and the second polymeric material (b).

  In one example, the composite shape memory material may comprise a first polymer layer comprising polycaprolactone polyester and a second polymer layer comprising polyurethane. The polycaprolactone polyester and polyurethane can be coextruded to form at least first and second polymer layers of a composite shape memory material. In another example, the composite shape memory material may comprise a first polymer layer comprising polyethylene and a second polymer layer comprising poly (ethylene terephthalate glycol). In yet another example where the composite shape memory material has a triple shape memory, the composite comprises a first polymer layer comprising polycaprolactone, a second polymer layer comprising polyurethane, and a third polymer layer comprising polyethylene. It may be. Polycaprolactone polyester, polyurethane, and polyethylene can be coextruded to form the first, second, and third polymer layers of the composite shape memory material.

  The shape memory material may be a filler (eg, inorganic filler) or other active material (eg, shape memory alloy wire, magnet sensitive filler, electroactive filler, light sensitive organic dye, and / or Others) may also be included. The filler may be a reinforcing filler (which improves the mechanical strength of the shape memory material), for example an active filler (which may contribute to the initiation mechanism of the shape memory effect), such as magnetic or conductive particles, or of a shape memory material It should be understood that it may be an active filler that may contribute to the improvement of other physical properties such as its thermal conductivity. The shape memory material may also contain UV screening agents, colored pigments, or other additives suitable for specific applications.

  The polymer composite shape memory materials described herein can be used in industrial applications by multi-layer coextrusion melt processing without the use of volatile solvents, toxic solvents, non-environmentally conscious solvents, and generally flammable liquid solvents. Can be manufactured on a large scale. The multilayer coextrusion can be a continuous process performed completely without the aid of a solvent. Also, when using commercially available homopolymers, copolymers, and multi-block systems instead of specially synthesized copolymers, less chemical synthesis is required. This layered structure mimics the phase separation structure of shape memory copolymers. The degree of shape recovery can be controlled by the polymer selected and the composition of the permanent material structure.

  Coextrusion is generally used to produce materials with thick layers (a few micrometers). Using a multilayer coextrusion process with layer multiplication, offset composition, gradient structure, and surface layer allows the production of films, strands or fibers with thin layers. Also, manufacturing shape memory materials that include layers of different thicknesses (20 nm to several tens of micrometers) potentially allows for changes in memory, deformation, and recovery behavior.

  In some embodiments, as illustrated in FIG. 2, the polymeric composite shape memory material is a multi-layer material 20 that exhibits shape memory behavior between a permanent shape 26 and an immobilized or temporary shape 28. It may be. The multilayer material comprises two alternating first polymer layers (A) 22 and second polymer layers (B) formed from a first polymer component (a) and a second polymer component (b), respectively. ) 24 (for example, ABAB...). In some examples, the multilayer shape memory material comprises at least 10 alternating layers (A) and (B), preferably from about 20 to about 500,000 (including any number increasing in these ranges). Alternate layers can be provided.

Each of layers (A) 22 and (B) 24 may be a microlayer or a nanolayer. The first polymer component (a) and the second polymer component (b) exhibit different glass transition and / or melting temperatures and are of the formula (AB) _x , where x = (2) ⁿ , where n is Multi-layer polymer composite sheet or film represented by the number of multiplier elements and in the range of 1-18. In other embodiments, alternating first polymer layer (A) 22 and second polymer layer (B) 24 may be represented by the formula (ABA) _x or (BAB) _x , where x = (2) ⁿ +1. Where n is the number of multiplier elements and is in the range of 0-18). Furthermore, the polymer components (a) and (b) have different heat due to secondary physical differences such as conformational differences between macromolecular structures, differences due to different processing conditions, differences in orientation or molecular weight. Chemically identical materials can be used as long as separate layers can be formed that exhibit the desired glass transition and / or melting temperature.

  In some embodiments, the first polymer (a) and the second polymer (b) are independently selected so long as the polymer composite multilayer shape memory material so formed exhibits shape memory behavior or properties. , Glassy polymeric materials, crystalline polymeric materials, rubbery polymeric materials or mixtures thereof. As an example, when the first polymer (a) is a glassy material, the second polymer (b) may be a rubbery material, a glassy material, a crystalline material, or a blend thereof. Alternatively, when the first polymer (a) is a rubbery material, the second polymer (b) may be a rubbery material, a glassy material, a crystalline material, or a blend thereof.

  In some embodiments, the first polymer layer (s) is a confined crystallization layer sandwiched between second polymer layers. The confined crystallized layer (s) can be formed by forced coextrusion of the first crystalline polymer material and the second polymer material. The co-extruded first crystalline polymer material can form a plurality of first crystallized polymer layers that are confined or sandwiched between second polymer layers.

  The thickness of each first confined crystallized layer may be such that each first layer forms a substantially crystalline lamella. Substantially crystalline lamellae wherein each first polymer layer is at least about 60% crystalline, at least about 70% crystalline, at least about 80% crystalline, at least about 90% crystalline, at least about 95% It means crystalline, or at least about 99% crystalline. This thickness may be on a nanoscale level, for example, from about 5 nanometers to about 1000 nanometers, from about 10 nanometers to about 500 nanometers, or from about 10 nanometers to about 20 nanometers. The thickness of each first layer depends on the particular polymer material used to form the first layer and is easily adapted to optimize crystallization properties (ie, forming high aspect ratio lamellae). You can choose. In one aspect of the invention, the thickness of the first layer should be such that a high aspect ratio crystalline lamella is formed in each first layer, It should not be so thin that it collapses easily, i.e. breaks, during coextrusion or after confinement.

  The thickness of the individual second layer used to confine the first layer may be at the nanoscale level. The thickness of these layers can be, for example, from about 5 nanometers to about 1000 nanometers, from about 10 nanometers to about 500 nanometers, or from about 10 nanometers to about 100 nanometers.

  Alternatively, the polymeric multilayer shape memory material may comprise more than two different polymer components, for example, when it is desired to form a shape memory material having a triple shape memory. For example, the three-component structure (eg, ABCABCABC...) Of alternating layers (A), (B), and (C) of components (a), (b), and (c), respectively, is (ABC) x (Wherein x is as defined above). Structures comprising any number of different component layers in any desired arrangement and combination, such as (CACBCACBC...) Are included within the scope of the present invention.

It should be understood that the multilayer structure may comprise additional types of layers. For example, these layers can include bonding layers, adhesive layers, and / or other polymer layers. The components of the various alternating layers may be the same or different. For example, the three-component structure (ABCABCA ...) of alternating layers of components (a), (b) and (c) is represented by (ABC) _x , where x is as defined above. expressed.

  The multilayer shape memory material can be produced by coextrusion of two polymer materials. Traditionally, shape memory materials are often made by solvent-based processes. These techniques are expensive, very toxic, and not environmentally friendly. The proposed new process is a safe and non-toxic process that can potentially eliminate all solvents. The coextrusion of the shape memory material is a high-speed continuous process capable of producing a large amount of materials having various structures in a short time. Melt extrusion can also provide a method for producing polymeric shape memory materials from commercially available polymers, eliminating the need for unique synthetic processes.

A typical multi-layer coextrusion apparatus is illustrated in FIGS. The two component (AB) coextrusion system consists of two 3/4 inch single screw extruders each connected to a coextrusion feedblock by a melt pump. This feed block for a two-component system combines the polymeric material (a) and the polymeric material (b) into the (AB) layer configuration. The melt pump controls two melt streams that are combined as two parallel layers within the feedblock. By adjusting the speed of the melt pump, the relative layer thickness, ie the ratio of A to B, can be changed. From the feed block, the melt passes through a series of multiplication elements. The multiplication element first slices the AB structure vertically and then widens the melt horizontally. The fluid stream recombines and doubles the number of layers. A collection of n multiplier elements creates an extrudate having a layer arrangement (AB) _{x where} x is (2) ⁿ equal to n and n is the number of multiplier elements. Those skilled in the art will appreciate that the number of extruders used to fabricate the structure of the present invention is equal to the number of components. Therefore, a three-component multilayer (ABC ...) requires three extruders.

  The multilayer shape memory material produced by the extrusion process may have at least two layers, including at least 10, 50, 100, or 1000 layers, including any number within that range. In one example, the multilayer shape memory material has 50 to 10,000 layers. In another example, the multilayer shape memory material is in the form of a film or sheet. By keeping the film or sheet thickness constant, the thickness of individual layers can be controlled by changing the relative flow rate or number of layers. The multilayer film or sheet may have an overall thickness in the range of 10 nm to 1000 μm, preferably in the range of 100 nm to 200 μm, and any numerical value that increases within that range. Furthermore, the multilayer film can be formed into a large number of articles by, for example, thermoforming, vacuum forming, or pressure forming.

  The polymeric multilayer shape memory material can be used to produce products for use in biomedical applications. For example, sutures, orthodontic materials, bone screws, nails, plates, meshes, prosthetic devices, pumps, catheters, tubes, films, stents, orthopedic fixtures, battenes, cast tapes, and tissue engineering scaffolds Ford, implants, and thermal indicators are manufactured.

  The polymer multilayer shape memory material can be molded into an implant material having a shape that can be implanted in the body and perform a mechanical function. Examples of such implants include rods, pins, screws, plates and anatomical shapes. A particularly preferred use of the above composition is the manufacture of sutures, which have a sufficiently rigid composition and can be easily inserted, but soften and reach the patient's comfort while reaching body temperature while still being A second shape is formed that allows healing.

  The polymer multilayer shape memory material has many uses other than biomedical applications. These applications include bumpers and other automotive body parts, food packaging, internal combustion engine auto chokes, polymer composites, fabrics, pipe fittings, heat shrink tubing, clamping pins, temperature sensors, damping materials, sports equipment, Examples include members that require deformation recovery after impact absorption, such as toys, single pipe binders, pipe inner laminates, lining materials, and clamping pins.

  In some embodiments, the molded article is a stop, including eyelets and rivets. The rivet may comprise a longitudinally deformed cylinder that can be inserted into an object or workpiece having an aperture therethrough. When heated, the deformed cylinder contracts in the longitudinal direction and expands in the lateral direction. The permanent shape of the stop and the radius of the deformed shape can be inserted into the workpiece, but are selected to expand and fill and clamp the workpiece. In addition, the longitudinal deformation (elongation) of the stop can be selected such that the stop imparts compression to the workpiece upon recovery to a permanent shape.

Example In this example, polyurethane (PU) was coextruded with polycaprolactone (PCL) to produce a shape memory material with switching based on melting temperature. The coextruded PU / PCL strands and films had 64 or 512 layers. For 64-layer strands or films, the layer thickness was 2.2 μm to 5.2 μm. For 512-layer strands or films, the layer thickness was 0.05 μm to 0.4 μm. The composition (volume / volume) varied PU / PCL at 30/70, 50/50, and 70/30.

  Poly (ethylene octane) (EO) was coextruded with poly (ethylene terephthalate glycol) (PETG) to produce a shape memory material with switching based on glass transition temperature. The coextruded PETG / EO strands and films had 64 or 512 layers. For 64-layer strands or films, the layer thickness was 2.2 μm to 5.2 μm. For 512-layer strands or films, the layer thickness was 0.05 μm to 0.4 μm. The composition (volume / volume) was changed by PETG / EO at 30/70, 50/50, and 70/30.

The properties of the PU / PCL shape memory material and the PETG / EO shape memory material are shown in Table 1.

  A strand of polycaprolactone (PCL) / polyurethane (PU) multilayered shape memory material comprising 512 alternating layers with 30/70 and 70/30 PCL / PU compositions is illustrated in FIG. FIG. 5 shows that the PCL / PU multi-layer strand is immobilized in a temporary shape and can be restored to its original strand shape with little or no permanent deformation of the sample.

  A film of polycaprolactone (PCL) / polyurethane (PU) multilayer shape memory material with 512 alternating layers having a 50/50 PCL / PU composition is illustrated in FIG. FIG. 6 shows that the PCL / PU multilayer film is fixed in a temporary shape and can be restored to its original film shape.

The multilayer film of FIG. 6 was exposed to a thermomechanical period, stress, and strain, and the restoration rate was measured. The results are shown in Table 2 and FIGS. FIG. 7 (AB) shows that the thermomechanical period improves the shape recovery of the micro-layered film with little effect on the shape fixation rate.

512 alternating alternating films prepared from various PCL / PU melt blends with varying PCL / PU ratios with varying PCL / PU ratios in the films at 30/70, 50/50, and 70/30 Compared to a multilayer film with a PCL / PU layer. The effect of the composition on the switching temperature was plotted and compared. Figure 8 (A-B) is different from the copolymer and the melt blend, the composition of the multi-layer PCL / PU film indicates that little effect on _{(T m} of PCL) switching temperature.

  Strands of PETG / EO multilayered shape memory material comprising 512 alternating layers with 30/70 and 70/30 PETG / EO compositions are illustrated in FIGS. 9A-B. FIG. 9 (AB) shows that the PETG / EO multilayer strand is immobilized in a temporary shape and can be restored to its original strand shape with little or no permanent deformation of the sample.

A film of PETG / EO multilayered shape memory material comprising a 50/50 PETG / EO composition and 512 alternating layers with film thicknesses of 310 nm and 90 nm, respectively, was subjected to thermomechanical cycles and stress, strain. The restoration rate was measured. The results are shown in Tables 3 and 4 and FIGS. FIG. 10 (AB) shows that shape fixing and recovery are particularly good with thinner layers and improve slightly with the thermomechanical period.

  FIG. 11 illustrates an example of a triple shape memory film of polycaprolactone (PCL) / polyurethane (PU) / polyethylene (PE) multilayered shape memory material. The triple shape memory material exhibits two temporary shapes due to two separate transitions in which each shape is formed.

  While the preferred embodiment of the invention has been illustrated and described, it should be understood that the invention is not limited to this embodiment. Numerous modifications, changes and variations will become apparent to those skilled in the art without departing from the scope of the invention as set forth in the claims below. All patents, publications, and references cited herein are incorporated by reference in their entirety.

Claims (27)

A multilayered composite shape memory material comprising a first polymer layer of a co-extruded first polymer material and a second polymer layer of a second polymer material,
The first polymeric material and the second polymeric material have different melting and / or glass transition temperatures, and the composite shape memory material after thermomechanical programming changes from at least one temperature-induced temporary shape to a permanent shape. A shape in which the first polymer layer constitutes a hard segment of the shape memory material that gives the shape memory material a permanent shape and the second polymer layer gives a temporary shape to the shape memory material A multilayered composite shape memory material comprising a switching segment of the memory material.   The material of claim 1, comprising a plurality of alternating first polymer layers and second polymer layers.   The material of claim 2 comprising at least 10 alternating first and second polymer layers.   The material of claim 1, wherein the first polymeric material is incompatible or partially compatible with the second polymeric material.   The material of claim 1, wherein the first polymer layer causes an elastic recovery of the shape memory material from a temporary shape to a permanent shape upon heating of the shape memory material above the switching temperature of the second polymer layer.   The material of claim 1, wherein the first polymer layer and the second polymer layer have an average thickness of about 10 nm to about 50 μm.   The material of claim 1, wherein the first polymeric material and the second polymeric material are not shape memory polymers.   The material of claim 1, wherein the first polymeric material comprises polyurethane and the second polymeric material comprises polycaprolactone.   The third polymer layer of claim 3, further comprising a third polymer layer of the third polymer material, wherein the third polymer layer constitutes a second switching segment of the shape memory material that provides the second temporary shape to the shape memory material. The materials described. Co-extrusion of a first polymeric material having a first glass transition or melting temperature and a second polymeric material having a second glass transition temperature different from the first glass transition or melting temperature to form a multilayer molded memory material A method for producing a multilayer shape memory material comprising:
A method of manufacturing a multilayer shape memory material, wherein the multilayer shape memory material after thermomechanical programming can undergo a shape transition from a temporary shape to a permanent shape due to at least one temperature induction.   The method of claim 10, wherein the multilayered shape memory material comprises alternating first polymer layers and second polymer layers.   The method of claim 1, wherein the multilayered shape memory material comprises at least 10 alternating coextruded first polymer layers and second polymer layers.   11. The method of claim 10, wherein the first polymeric material is incompatible or partially compatible with the second polymeric material.   The method of claim 11, wherein the first polymer layer causes an elastic recovery of the shape memory material from a temporary shape to a permanent shape upon heating of the shape memory material above the switching temperature of the second polymer layer.   The method of claim 10, wherein the first polymer layer and the second polymer layer have an average thickness of about 10 nm to about 50 μm.   The method of claim 10, wherein the first polymeric material and the second polymeric material are not shape memory polymers.   11. The method of claim 10, wherein the first polymeric material comprises polyurethane and the second polymeric material comprises polycaprolactone.   A third polymer material is further coextruded with the first polymer material and the second polymer material to provide a shape memory material having a third polymer layer, the third polymer layer being in the shape memory material a second temporary material. The method of claim 11, comprising a second switching segment of shape memory material that provides a geometric shape. A multilayer shape memory material comprising a co-extruded and multilayered mechanically deformable composite shape memory sheet,
The multilayered mechanically deformable composite shape memory sheet is of the formula (AB) _x , where x = 2 ⁿ and n is in the range of 1-18, a plurality of at least two alternating Comprising layers (A) and (B);
Layer (A) consists of polymer component (a), layer (B) consists of polymer component (b); and polymer components (a) and (b) have different glass transition and / or melting temperatures, A multilayer shape memory material in which the multilayer shape memory material after mechanical programming is capable of undergoing a shape transition from a temporary shape to a permanent shape due to at least one temperature induction.   20. A material according to claim 19, comprising at least 10 alternating polymer layers.   20. A material according to claim 19, wherein the polymer component (a) is incompatible or partially compatible with the polymer component (b).   20. The material of claim 19, wherein the polymer layer (A) causes an elastic recovery of the shape memory material from a temporary shape to a permanent shape upon heating of the shape memory material above the switching temperature of the polymer layer (B).   20. The material of claim 19, wherein the polymer layer (A) and the polymer layer (B) have an average thickness of about 10 nm to about 50 [mu] m.   20. A material according to claim 19, wherein the polymer component (a) and the polymer component (b) are not shape memory polymers.   20. A material according to claim 19, wherein the polymer component (a) is polyurethane and the polymer component (b) is polycaprolactone.   20. A polymer layer (C) comprising a polymer component (c), further comprising a polymer layer (C) constituting a second switching segment of a shape memory material that imparts a second temporary shape to the shape memory material. Materials described in.   20. The material according to claim 19, wherein the polymer component (a) and the polymer component (b) have different melting temperatures and / or glass transition temperatures.

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